1. Field of the Invention
This invention relates to both a tool and a method used in the drilling of a workpiece, and in particular a workpiece of composite material, such as resin impregnated composite material. The tool is reusable, while the drilling is produced by another tool which is known.
2. Prior Art
The use of composite material, such as resin impregnated composite material in the aircraft industry is now commonplace. As its use increases, the need to adapt the material also increases. For example, the need to drill composite materials arises, and while drilling may seem to be a routine manufacturing procedure, when dealing with composite materials such as resin impregnated composite materials, the procedure frequently results in problems. For example, the problem of break-out when drilling holes through composite material frequently arises. Because of the nature of composite materials, i.e., those composite materials having fibers or filaments embedded in a resin matrix, the passage of a drill produces at the exit-end of the hole (break-out) dislocations in the form of de-laminations of the fibers and resin. A de-lamination in a composite material can be quite serious as the de-lamination propagates outwardly from the hole into the material. Then, if the material so de-laminated is used as a load bearing part, the potential for structural failure arises with, in particular in the aircraft industry, possible catastrophic consequences.
One solution is to avoid drilling the composite material. This is not always possible, however, considering the increased demand to use such material because of its weight and load redundancy advantages.
It would, therefore, be desirable to have a way of drilling composite material where break-out de-lamination did not occur.
No satisfactory way to solve the noted problem using known techniques could be found.